The present disclosure relates to a signal processing apparatus and a signal processing method. More particularly, the present disclosure relates to a signal processing apparatus typically capable of reproducing a carrier by making use of a circuit having a small size and capable of reducing the power consumption and relates to a signal processing method provided for the apparatus.
In radio communication, for example, a transmitting apparatus modulates a carrier in accordance with data to be transmitted as an object of the transmission and then transmits a modulated signal obtained as a result of the modulation by adoption of the radio communication technique. Then, a receiving apparatus detects the modulated signal in order to convert the modulated signal into a baseband signal and, then, demodulates the baseband signal in order to obtain received data corresponding to the transmitted data.
There are a variety of methods adapted to detect a modulated signal. Typical examples of the methods are synchronous detection (or product detection), square-law detection and envelope detection. In order to adopt the synchronous detection, in the receiving apparatus, it is necessary to reproduce a carrier synchronous to the carrier used in the transmitting apparatus.
A carrier obtained as a result of reproduction of a carrier synchronous to the carrier used in the transmitting apparatus is referred to as a reproduced carrier.
A typical example of the method to reproduce a carrier is a method adopting a frequency multiplication technique. For more information on the method adopting a frequency multiplication technique (refer to documents such as Japanese Patent Publication No. Hei 06-042684 and Japanese Patent Publication No. Hei 06-012902).